1. Field of the Invention
The present invention relates to a transmission device which can transmit power imparted to an input shaft to an output shaft while changing a speed by switching an engagement side frictional engagement element which is at least one of a plurality of hydraulic frictional engagement elements, each of which operates with hydraulic pressure from a hydraulic control unit, from a released condition to an engaged condition, and to a control method thereof.
2. Description of the Related Art
To date, as a control unit of this kind of transmission device, there has been known one which, when instructed to execute a clutch-to-clutch speed change wherein a speed change is achieved by a release of a release side frictional engagement element and an engagement of an engagement side frictional engagement element, detects a speeding up of a power source, wherein an actual rotation speed of the power source rises higher by a predetermined value or more than a rotation speed calculated from a rotation speed of an output shaft of a transmission device and a speed change ratio before the speed change, and when detecting the speeding up, learns and corrects a constant pressure standby pressure, a fast fill time, and the like, of the release side frictional engagement element and engagement side frictional engagement element (for example, refer to JP-A-2008-25624). This transmission device control unit obtains a speeding start time from the instruction to execute the clutch-to-clutch speed change until the start of the speeding up, and based on the speeding start time, determines which one of the release side frictional engagement element and engagement side frictional engagement element causes the speeding up. Then, this control unit, in order that a speeding up or tie-up in the clutch-to-clutch speed change is smoothly resolved, carries out a learning and correction based on a determination result in such a way that a speeding cause side learning and correction value changes greatly in comparison with a non-cause side one, thus achieving a swift resolution of the speeding up or tie-up in the clutch-to-clutch speed change while suppressing a delay in conclusion due to a learning and correction value relating to a non-cause side frictional engagement element increasing unnecessarily.